Methods:
Patients were randomly divided to receive 1 PI drop starting 2 minutes before the last swab (PI group) or 3 drops starting 30 minutes before the last swab (PIplus group). Conjunctival swab was obtained five minutes before, and 30 minutes after the first povidone iodine drop was instilled into the conjunctival sac. Corneal paquimetry was performed before and after procedure using OcuScan Alcon RXP (Alcon, Fortworth, Texas). Conjunctival swabs were incubated aerobically in enriched Thioglycolate liquid medium (meat broth) and in three solid culture media (Agar Chocolate, Trypticase Soy Agar with 5% sheep blood, and Agar Sabouraud).

Results:
A total of 120 patients (120 eyes) were included: 59 eyes in the group PI and 61 in PIplus. There were no significant differences between groups regarding age and gender. A similar proportion of patients had microorganisms isolated from the conjunctival swab before treatment: 18/61 (29.5%) for PIplus group and 14/59 (23.7%) for PI group (P=0.5386). Also, no significant difference was found for the number of positives cultures that became negative after treatment between groups (p=0.4225). When comparing groups, a similar proportion of positive cultures after treatment was found, 9/61 (14.7%) for PIplus group and 12/59 (20.3%) for PI group (P=0.4768), relative risk of 0.7254 (CI95%= 0.3303 to 1.593). Staphylococcus epidermidis were the most frequently isolated microorganisms in cultures from both groups. Mean corneal thickness didn’t change significantly in both groups after treatment.

Conclusions:
This data indicates that using 3 drops 30 minutes before or 1 PI drop 2 minutes before are associated with similar redunction of conjunctival bacterial flora.